1. Field of the Invention
The present invention relates to an information recording apparatus and an information recording method, an information reading apparatus and an information reading method, a magnetic tape format, and a recording medium. More particularly, the present invention relates to an information recording apparatus and an information recording method, an information reading apparatus and an information reading method, a magnetic tape format, and a recording medium, by which an entire display screen can be roughly displayed when some of the search data is lost due to tag recording and/or editing, during a pull-in of tracking control for tracing search data, and also when an error occurs during reading.
2. Description of the Related Art
FIG. 1 is a block diagram showing the construction of a conventional recording/reading apparatus 1. Here, a description is given of a case in which, as a representative example, search image data for an 8×-speed search is arranged and displayed with respect to data such that a video of 1440×1080/60i is compressed in accordance with MP@H-14 where N=15 (that is, 1 GOP (Group of Pictures) is formed of 15 frames).
A microcomputer 11 controls the recording/reading apparatus 1 in accordance with a signal indicating an operation of a user, which is input from an input section 12. The microcomputer 11, for example, generates a control signal for creating a search image in order to output it to a search data creation section 23, generates a control signal for displaying a search image in order to output it to a search image display section 37, generates a control signal for selecting data in order to output it to a switch 22, a switch 35, or a switch 38, and generates a control signal for moving a magnetic tape 30 in a forward/reverse direction in order to outputs it to a capstan motor 15.
A dial 13 and an operation button 14 are connected to the input section 12. The dial 13 is used such that a rotation operation and an operation for pressing in a direction at right angles to the rotation axis (to the right in the figure) are made possible, and is operated by a user. The operation button 14 is, for example, formed of various buttons, such as a recording button and a button for taking up the magnetic tape 30, and outputs a signal indicating the operation content of the user to the input section 12. The input section 12 outputs the signal indicating the operation of the user, which is input from the dial 13 or the operation button 14, to the microcomputer 11.
The capstan motor 15 drives the magnetic tape 30 in accordance with a control signal input from the microcomputer 11.
A video data compression processing section 21 compresses an input video signal in accordance with, for example, MP@H-14 of MPEG2, creates compressed data made up of a plurality of GOPs (GOP0, GOP1, . . . , GOPn) composed of 15 frames, formed of I pictures, B pictures, and P pictures, such as those shown in FIG. 2, and supplies the compressed data to the switch 22 and the search data creation section 23.
The search data creation section 23 creates search data from the compressed image data. That is, the search data creation section 23 extracts I pictures formed of intra-frames from among the I pictures, B pictures, and P pictures of the respective GOP, and creates search image data. From each I picture, search image data for one frame is created.
At this point, search image data created from I pictures in the search data creation section 23 is described with reference to FIG. 3. The number of effective pixels of luminance data of image data before encoding and after decoding is 1440 samples in the horizontal direction and 1080 samples in the vertical direction. Also, the number of effective pixels of color-difference data is 720 samples in the horizontal direction and 540 samples in the vertical direction. One screen of a search image for this image data, as shown in FIG. 3, is formed of 90(=1440÷16) macroblocks (MB) in the horizontal direction and 68 (=1080 ÷16 (rounding up to the next whole number)) macroblocks in the vertical direction. That is, one screen of a search image is formed of 6120 (90×68) macroblocks.
One macroblock is formed of 6 pieces of data of data in which DC components are extracted from each of the luminance signals Y which are divided into 4 DCT blocks of 8 pixels×8 pixels and are converted into 6 bits, and data in which DC components are extracted from each of the color-difference signals Cb and Cr of a DCT block of 8 pixels×8 pixels. That is, one macroblock is formed of 34-bit data.
An audio data compression processing section 24 compresses input audio data and outputs it to the switch 22. The switch 22 selects data from within the data from the video data compression processing section 21, the search data creation section 23, and the audio data compression processing section 24, and the input system data under the control of the microcomputer 11, and outputs it to the error code ID addition section 25.
The error code ID addition section 25 adds error-detection correction codes (parities) C1 and C2 and an ID to the input data, performs an interleaving process between 16 tracks thereon, and outputs it to the sync addition modulation section 26. The sync addition modulation section 26 adds a 16-bit sync pattern indicating the start of the packet to the input data, performs predetermined modulation thereon, and outputs the data to a P/S (Parallel/Serial) conversion section 27.
The P/S conversion section 27 converts the input data from parallel data into serial data, and outputs it to an amplifier 28. The amplifier 28 amplifies the input data and outputs it to a rotary head 29. The rotary head 29 is mounted on a rotary drum (not shown) and causes the input data to be recorded on the magnetic tape 30.
FIG. 4 shows an example of the arrangement of a search image data area for an 8x-speed search. Search image data for 17 sync blocks from SB(0) to SB(16) is inserted into one search image data area. The amount of search picture data of one sync block is 720 bits, and a maximum of 21 macroblocks of 34 bits is contained. Then, a plurality of search image data areas are arranged in such a way that at least 34 sync blocks can be obtained by one trace at intervals of 16 tracks, which are in ECC interleave units.
Then, as shown in FIG. 5, the search image data for 9 traces is arranged across 144 tracks. Here, dummy data is inserted as necessary on the 10th trace so that, on average, one GOP (15 frames) is recorded on the 150 tracks.
In a case where 34 sync blocks can be obtained in one trace, since the number of macroblocks obtained in 9 traces is 6426 macroblocks from 21×34×9, it is possible to obtain data for displaying one screen (composed of 6120 macroblocks) of a search image.
Referring back to FIG. 1, a process for reading data recorded on the magnetic tape 30 is described below.
The data recorded on the magnetic tape 30 is read as an analog electrical signal by the rotary head 29, and this signal is output to the amplifier 31 whereby it is amplified, and is output to an A/D conversion section 32. The A/D conversion section 32 converts the input analog electrical signal into digital data and outputs it to a demodulation section 33. The demodulation section 33 demodulates the input digital data and outputs it to an error-correction ID detection section 34. The error-correction ID detection section 34 performs error correction based on the error-detection correction codes C1 and C2, detects the ID, and performs a deinterleaving process.
Then, as for the data output from the error-correction ID detection section 34, based on a sync block header, the video data is output to the video data decompression section 36, the search image data is output to the search image display section 37, and the audio data is output to the switch 38, via the switch 35. Also, the subcode data and the AUX data are output as system data via the switch 35.
During normal reading, the video data decompression section 36 decompresses input video data, converts the data from digital data into analog data if necessary, and outputs it, via a switch 38, to a monitor 39 formed of, for example, a liquid-crystal panel, whereby the data is displayed. During a search, the search image display section 37 temporarily stores the obtained search data, performs image processing on the stored data in order to create search image data, and can store it in a buffer provided therein. The search image display section 37 converts the search image data stored in the buffer from digital data into analog data if necessary, and outputs it to the monitor 39 via the switch 38, on which the data is displayed.
Also, in a photo-taking mode, image data which is being taken from an image capturing section (for example, a CCD camera) (not shown) to the monitor 39, and the image data which is being taken by the image capturing section is displayed on the monitor 39.
The switch 38 performs a process for switching, under the control of the microcomputer 11, the data which is output to the monitor 39 and is displayed thereon between the data which is output from the video data decompression section 36 and the data which is output from the search image display section 37.
The audio data decompression section 40 decompresses the input audio data, converts the data from digital data to analog data if necessary, and causes the data to be output from a speaker 41.
However, in a case where new data is overwritten on recorded data as a result of editing and/or a tag recording being performed on the magnetic tape 30 on which data is prerecorded, for example, a GOP with 3 or 6 frames, which is shorter than a normal one, may occur. This is because a tag recording and/or editing in units of 3 frames are made possible in the recording/reading apparatus 1.
For example, when GOP1 is overwritten in the 4th and subsequent frames of GOP0, as shown in FIG. 6, the picture of GOP0, which is made to remain on the magnetic tape 30 after a tag recording and/or editing, becomes only the 3rd frame. Also, when GOP1 is overwritten on the 10th and subsequent frames of GOP0, as shown in FIG. 7, the picture of GOP0, which is made to remain on the magnetic tape 30 after a tag recording and/or editing, becomes only the 6th frame.
More specifically, in the cases shown in FIGS. 6 and 7, some of the search image data of GOP0, which is the lower part, to put it in detail, some of the ECC interleave units for 9 tracks, where the search image data is arranged, will be lost. In such a case, the search image to be displayed will become very poor, such as a part of the lower portion of the screen being not displayed.
Furthermore, during a pull-in of tracking control for tracing search data and also when an error occurs during reading, since search image data is not available for one screen, a case may occur in which a portion of the screen is not displayed.